Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 507 - diyAudio
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Old 14th August 2012, 05:32 AM   #5061
GM is online now GM  United States
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To change driver height, change Fs. To make it smaller, reduce Vas and/or Qts. As a general rule, I don't recommend making it any smaller than reducing 'Sm' to ~0.7x the calculated value.

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Old 14th August 2012, 12:54 PM   #5062
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GM,
Thank you for the informative responses, they are appreciated. What are the effects of reducing the Sm to less than .7 of a drivers calculated value?

Best,
Ed
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Old 14th August 2012, 04:07 PM   #5063
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Assuming you'll occasionally want to 'crank' it up and/or play some relatively dynamic recordings, then without a high pass, the odds are that the drivers will sooner than later be damaged and/or let their smoke out when they're called upon to reproduce any signal below ~0.8x Fs, which considering this driver's high Fs it would be while playing music from most any source recorded after stereo LPs came along in the late '50s.

Note that I've no personal experience with this driver and being designed for prosound apps I may be being overcautious, but better safe than sorry IMO.

Then there's amplitude modulation distortion [AMD] to consider that occurs when drivers used in a wide BW app are driven much beyond a few mm. Some folks can listen to, even enjoy, mass quantities of it, but in making recommendations I feel I should assume a worst case scenario, which is they are like me and find it intolerable for critical listening.

GM
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Old 14th August 2012, 04:36 PM   #5064
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Quote:
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Note that I've no personal experience with this driver and being designed for prosound apps I may be being overcautious, but better safe than sorry IMO.
GM
GM,
It is obvious you are knowledable in this area so I appreciate your opinions regardless of your experience with this particular driver. And yes, this being for my son means that it will get "cranked up" on a regular basis, so thanks for the warning.

It is becoming apparrent to me that I will likely need to go to a large and simple BR for this driver. That will allow me to build the box in ratios that can live in the space and still allow for some bass reproduction. I am considering a 5 cuft ported enclosure. What is the best freeware cabinet program available for me to calculate the port with, WinISD?

Thanks again for your thoughful responses.

Best,
Ed
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Old 14th August 2012, 05:54 PM   #5065
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You're welcome!

Your Qs moves them too far afield of a BIB alignment, so please start a new Beta12 LTA thread.

GM
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Old 18th August 2012, 08:33 PM   #5066
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To change driver height, change Fs. To make it smaller, reduce Vas and/or Qts. As a general rule, I don't recommend making it any smaller than reducing 'Sm' to ~0.7x the calculated value.

GM
I have noted that when changing FS to a lower value the box gets taller and more narrow. I initially set the FS to the drivers spec. When we lower FS are we actually changing the output of the speaker for a given driver? What is the tradeoff, lower power handling, lower SPL (edit, I believe you answered this in the post above, anything lower that .8 of the drivers FS will burn up the driver at lower frequencies, thanks.)? The SM number changes as well, from your previous post you recommend not letting the SM go less than .7 of the drivers calculated value, so I will use that as a stopping point, but it is nice to be able to modify the size of the cabinets w&d by increasing the height. I am sure there is a practical point that this can be done with regard to the ceiling height, can anyone tell me what that may be?

Thanks,
Ed
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Last edited by ebag4; 18th August 2012 at 08:45 PM.
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Old 18th August 2012, 09:32 PM   #5067
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Theres a thread on a 12lta in a bib, search bbbib.

Its a whopper and from what i heard it rocks.

When i get the funds and time its going to be the second bib i build.

The first one will be a pair around 2 CSS EL70 per cab for a cousin.
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Old 19th August 2012, 01:30 AM   #5068
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Well, it's getting tuned lower than the full octave below Fs of the default tuning, so with the same net Vb it will have a more extended LF, but with a faster roll off and a different harmonic structure that may/may not be beneficial once the room’s impact is factored in. Short of some serious room measurements though, there’s only one way to know for sure.

Correct, BIB tuning dictates an acoustically large net Vb to ensure a reasonable amount of power handling when corner loaded, so reducing it much might reduce it too much IF the room’s gain structure doesn’t add enough low end gain BW to offset it.

Well, I said it’s likely if played at high power without a high pass filter.

T.C.’s original BIB is ~70” tall and works fine with 8 ft ceilings, so at a glance it seems reasonable that it should be at least this tall plus it puts the driver at a good height for most apps.

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Old 26th September 2012, 07:51 PM   #5069
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triadtron playing on my big BIB - YouTube

I made a short video of a Triadtron-amp playing on one of my BIBs. Its a 1,3 watt single end hexfet amp from Tube CAD Journal. No global feedback and only two IRF9530s (i had them laying around).

The microphone in my camera is not good. I dropped my camera in a lake once...
I think one can hear that it has potential anyways. Both the BIBs and my small amp.

Johannes.
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Old 27th September 2012, 03:19 AM   #5070
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These the B&C?

GM
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